If-Range

The If-Range HTTP request header makes a range request conditional: if the condition is fulfilled, the range request will be issued and the server sends back a 206Partial Content answer with the appropriate body. If the condition is not fulfilled, the full resource is sent back, with a 200OK status.

This header can be used either with a Last-Modified validator, or with an ETag, but not with both.

The most common use case is to resume a download, to guarantee that the stored resource has not been modified since the last fragment has been received.

Syntax

Directives

<etag>

An entity tag uniquely representing the requested resource. It is a string of ASCII characters placed between double quotes (Like "675af34563dc-tr34") and may be prefixed by W/ to indicate that the weak comparison algorithm should be used.